In a video posted on their Instagram account, the couple’s three children, George, Charlotte and Louis, can be seen playing on the swing, by a wooden den, and scrambling barefoot through a stream. Louis, who celebrated his first birthday last month, can be seen walking for the first time and waving a stick.

Kate said she had been focusing on early childhood development in her recent charity work.

“I believe that spending time outdoors when we are young can play a role in laying the foundations for children to become happy, healthy adults,” she said.

The Chelsea Flower Show, which is open to the press and guests on Monday and to the public from Tuesday to Saturday, is the most prestigious event in Britain’s gardening calendar.

Britain’s Prince William and Catherine, Duchess of Cambridge with Prince George and Prince Louis explore the Adam White and Andree Davies co-designed garden ahead of the RHS Chelsea Flower Show in London, Britain. May 19, 2019. Picture taken May 19, 2019. Matt Porteous/PA Wire/Handout via REUTERS.

Britain’s Princess Charlotte plays on a rope swing at the Adam White and Andree Davies co-designed garden ahead of the RHS Chelsea Flower Show in London, Britain. May 19, 2019. Picture taken May 19, 2019. Matt Porteous/PA Wire/Handout via REUTERS.

Britain’s Catherine, Duchess of Cambridge, looks at a display during her visit to the RHS Chelsea Flower Show at the Royal Hospital Chelsea, London Britian May 20, 2019. Yui Mok/Pool via REUTERS

Britain’s Catherine, Duchess of Cambridge, speaks with a visitor during her visit to her garden at the RHS Chelsea Flower Show at the Royal Hospital Chelsea, London Britian May 20, 2019. Yui Mok/Pool via REUTERS

Britain’s Catherine, Duchess of Cambridge, visits her garden at the RHS Chelsea Flower Show at the Royal Hospital Chelsea, London Britian May 20, 2019. Yui Mok/Pool via REUTERS

Britain’s Catherine, Duchess of Cambridge, is pictured with Andree Davies and Adam White during a visit to her garden at the RHS Chelsea Flower Show at the Royal Hospital Chelsea, London Britian May 20, 2019.

Yui Mok/Pool via REUTERS

Britain’s Catherine, Duchess of Cambridge, and Sir Nicholas Bacon, Chairman of the Royal Horticultural Society, are pictured at the RHS Chelsea Flower Show at the Royal Hospital Chelsea, London Britian May 20, 2019. Yui Mok/Pool via REUTERS

Britain’s Catherine, Duchess of Cambridge, attaches her message to a board during her visit to the RHS Chelsea Flower Show at the Royal Hospital Chelsea, London Britian May 20, 2019. Yui Mok/Pool via REUTERS

Britain’s Catherine, Duchess of Cambridge, writes a message to pin to a board during her visit to the RHS Chelsea Flower Show at the Royal Hospital Chelsea, London Britian May 20, 2019. Yui Mok/Pool via REUTERS